Cerebral Autoregulation (CA) is the physiological strategy used for the brain to maintain the cerebral blood flow constant during blood pressure (BP) changes. The evaluation of CA dynamic and static models has been described in the literature. The coefficient Sx and the Mx are one of the validated dynamic methods. These coefficients are obtained from the correlation between BP and Middle Cerebral Artery (MCA) velocity measured using Transcranial Doppler (TCD). Correlation values higher than 0.3 reflect an impairment of CA.